The 1990s were not a great decade for railroads in Atlantic Canada & New England, but they weren’t as terrible as the 1980s, and the modest uptick in business plus electrifying parts of the D&H and BAR plus some of the really old class B motors starting to reach the point where the Portland shops couldn’t keep them running meant that a bunch of new motors were needed.
22 new class J2 motors helped, and the solitary FF3 didn’t hurt, but the railroad wanted something to fill the gap between the superpower motors and the regular road switchers; the class K streamliners filled that gap.
B+B+B wheel arrangements are not rare, except for North America, but the mechanical arrangements for a 6500hp AC drivetrain turned out to be just a little too big for a single class B motor and a little too small for an articulated unit like the class Is.
So this unit; a double-ended motor (one comfort cab, one hostler cab) on 3 low profile trucks, tucked into a streamlined carbody approximately the same size as an EMD FL-9.
There have been ten variants of the class K; the OG streamlined cab, the multi-system rebuilds of the K1, the hood unit 707, the more-conventionally laid out K2, the K3 for Amtrak’s Alouette, the ILW-built K4, the multi-system K5 for the D&H South electrification, the ILW-built Draper Tapered K6, and the “pocket-L” K7s & (ILW-built) K8s.
92 have been built; all are in service.